Irrigation systems utilize a series of pipes or conduits for conveying water from a water source to a series or network of water emitters or sprinklers. Irrigation system components are typically installed and operate below ground level, which may cause rocks, dirt, and other debris to enter the irrigation system and travel along the pipes with the water flow. Contamination, particularly in the form of particulate matter, can impair the operation of components within the irrigation system. To protect a component, such as a valve, from particulate matter, some irrigation systems utilize a screen disposed at the inlet of the valve. However, a valve using such an approach suffers from a significant shortcoming in that a user must disconnect the valve from the upstream and downstream pipe in order to service the valve. Commonly, the pipes are threadingly engaged with the valve and must be rotated to disconnect the pipe from the valve. This operation may be difficult and time consuming if the valve and the upstream pipe are in narrow confines or are otherwise limited in their range of movement.
One approach to creating a more easily serviceable connection between a pipe and a valve is to use a union coupling. A union coupling has a pair of fittings or joints that may connect to other irrigation system components, such as the pipe and the valve. The union coupling further comprises a collar that is rotated or otherwise manipulated to draw the fittings together and form a connection therebetween. One type of existing union coupling includes a fitting having an annular ridge extending around one end of the fitting to restrict the collar from sliding off of the fitting. However, the collar is free to slide off the other end of the fitting until that end is connected to the pipe or valve. This approach may be problematic during installation, as the fitting with the annular ridge can be accidently installed onto the pipe or valve without the collar. If pipe cement or other chemical bonding has been used, subsequent removal of the fitting from the pipe or valve may cause damage to the fitting and require replacement.
Another shortcoming of existing union couplings is that they are often unable to withstand loads applied to the side of the manifold. In greater detail, these types of manifolds have an annular ridge to retain a collar on each outlet of the manifold with the collars being used to connect the respective outlet to a fitting or hose. Irrigation manifolds are assembled by passing a collar of the union coupling over the outlet and urging an inwardly projecting lip of the collar against the annular ridge of the manifold until it is forced beyond the ridge. Once the lip has been forced past the annular ridge, the interference between the lip and the annular ridge restricts the collar from falling off the manifold outlet. Because the annular ridge has to be small enough to permit the lip of the collar to snap beyond the annular ridge, the ability of the ridge to restrict the collar from falling off of the outlet is necessarily less than optimal. Accordingly, when a side load is applied to the manifold, the resulting bending moment between a manifold outlet and the corresponding fitting tends to cause the collar to snap past the annular ridge and off of the manifold outlet.
Yet another disadvantage of existing union couplings is manifest in typical plumbing installations using polyvinyl chloride (PVC) pipes. Specifically, one common approach to installing a union coupling with PVC pipes involves using a series of fittings interconnected by short pieces of pipe. For example, if a PVC pipe is to be connected to a valve, an installer would use: 1) a slip fitting for connecting to the end of the PVC pipe; 2) a union coupling including two fittings and a collar; 3) a male threaded adapter for connecting to the valve inlet; 4) a short piece of PVC pipe to connect the slip fitting to the union coupling; and 5) a short piece of PVC pipe to connect the union coupling to the male threaded adapter. Although the series of fittings and PVC pipes would be relatively rigid once connected, the overall size of the installation is very large and labor-intensive to assemble. Further, it is problematic to keep all of the fittings and PVC piping on hand for what is essentially a custom installation for each valve.